code: def timeout_timer(self):
      while True:
          time.sleep(remote_constants.HEARTBEAT_INTERVAL_S)
  
          if (self.host_pid is not None) and (
              not psutil.pid_exists(self.host_pid)
          ):
              self.exit()
  
          if self.exit_flag:
              break
  
          if (
              time.time() - self.last_heartbeat_time
              > remote_constants.HEARTBEAT_RCVTIMEO_S
          ):
              # heartbeat exit
              break
  
imports: import grpc
  import os
  import time
  import threading
  from concurrent import futures
  from parl.remote import remote_constants
  from parl.remote.grpc_heartbeat import heartbeat_pb2
  from parl.remote.grpc_heartbeat import heartbeat_pb2_grpc
  from parl.utils import logger, get_ip_address
  import psutil
  import multiprocessing
label_desc: Use image node_id 4 for calling the GrpcHeartbeatServer obj's underlying member method code with example usage: obj.timeout_timer() without return types